Abstract-This paper proposes a new approach to simplify the two-dimensional random walk models capturing the movement of mobile users in Personal Communications Services (PCS) networks. Analytical models are proposed for the new random walks. For a PCS network with hexagonal configuration, our approach reduces the states of the two-dimensional random walk from (3 2 + 3 5) to ( + 1) 2, where is the layers of a cluster. For a mesh configuration, our approach reduces the states from (2 2 2 + 1) to ( 2 + 2 + 4) 4 if is even and to ( 2 + 2 + 5) 4 if is odd. Simulation experiments are conducted to validate the analytical models. The results indicate that the errors between the analytical and simulation models are within 1%. Three applications (i.e., microcell/macrocell configuration, distance-based location update, and GPRS mobility management for data routing) are used to show how our new model can be used to investigate the performance of PCS networks.

This paper presents a study of channel occupancy times and handoff rate for mobile computing in MC (Mobile Computing) and PCS (Personal Communications Services) networks, using general operational assumptions. It is shown that, for exponentially distributed call holding times, a distribution more appropriate for conventional voice telephony, the channel occupancy times are exponentially distributed if and only if the cell residence times are exponentially distributed. It is further shown that the merged traffic from new calls and handoff calls is Poisson if and only if the cell residence times are exponentially distributed, too. When cell residence times follow a general distribution, a more appropriate way to model mobile computing sessions, new formulae for channel occupancy time distributions are obtained. Moreover, when the call holding times and the cell residence times have general (nonlattice) distributions, general formulae for computing the handoff rate during a call connection and handoff call arrival rate to a cell are given. Our analysis illustrates why the exponential assumption for call holding time results in the underestimation of handoff rate, which then leads to the actual blocking probabilities being higher than the blocking probabilities for MC/PCS networks designed using the exponential distribution approximation for call holding time. The analytical results presented in this paper can be expected to play a significant role in teletraffic analysis and system design for MC/PCS networks.

Natriuretic peptides (NPs) have been found to be useful markers in differentiating acute dyspneic patients presenting to the emergency department (ED) and emerged as potent prognostic markers for patients with congestive heart failure (CHF). The best-established and widely used clinical application of BNP and NT-proBNP testing is for the emergent diagnosis of CHF in patients presenting with acute dyspnea. Nevertheless, elevated NPs levels can be found in many circumstances involving left ventricular (LV) dysfunction or hypertrophy; right ventricular (RV) dysfunction secondary to pulmonary diseases; cardiac inflammatory or infectious diseases; endocrinology diseases and high output status without decreased LV ejection fraction. Even in the absence of significant clinical evidence of volume overload or LV dysfunction, markedly elevated NP levels can be found in patients with multiple comorbidities with a certain degree of prognostic value. Potential clinical applications of NPs are expanded accompanied by emerging reports regarding screening the presence of secondary cardiac dysfunction; monitoring the therapeutic responses, risk stratifications and providing prognostic values in many settings. Clinicians need to have expanded knowledge regarding the interpretation of elevated NPs levels and potential clinical applications of NPs. Clinicians should recognize that currently the only reasonable application for routine practice is limited to differentiation of acute dyspnea, rule-out-diagnostic-tests, monitoring of therapeutic responses and prognosis of acute or decompensated CHF. The rationales as well the potential applications of NPs in these settings are discussed in this review article.

Mobility management in Long Term Evolution (LTE) is different from that in the third generation mobile telecom networks. In LTE, the Mobility Management Entity (MME) is responsible for the mobility management function. The MME is connected to a large number of evolved Node Bs (cells) that are grouped into the Tracking Areas (TAs). The TAs are further grouped into TA Lists (TALs). When a User Equipment (UE) moves out of the current TAL, it reports its new location to the MME. If the LTE network attempts to connect to the UE, the MME asks the cells in the TAL to page the UE. In LTE paging, the MME may sequentially page a cell, the TA of the cell, and/or TAL of the cell. This paper investigates the performance of LTE paging, and provides the guidelines for the best paging sequence of cells.

PurposeSevere hypoglycemia can result in neural damage, impaired cognitive function, coma, seizures, or death. The decision to admit diabetic patients after initial treatment in the emergency department remains unclear. Our purpose is to identify risk factors for developing recurrent hypoglycemia in diabetic patients admitted for severe hypoglycemia.Materials and MethodsWe reviewed the records of 233 subjects (92 males, 141 females; mean age, 74.1 ± 9.8 years) with type 2 diabetes treated at a tertiary care teaching hospital and hospitalized for severe hypoglycemia.ResultsSeventy-four (31.8%) patients were categorized with recurrent hypoglycemia and 159 (68.2%) with non-recurrent. Multivariate logistic regression analysis revealed that patients with loss of a recent meal, coronary artery disease, infection, and poor renal function (lower estimated glomerular filtration rate) were at risk for recurrent hypoglycemia. The use of calcium-channel blockers appeared to be a protective factor for the development of recurrent hypoglycemia.ConclusionThere may be a subset of patients with severe hypoglycemia and certain risk factors for recurrent hypoglycemia that should be admitted.

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In Long Term Evolution (LTE), the cells (the radio coverages of base stations) are grouped into the Tracking Areas (TAs), and the TAs are further grouped into the TA List (TAL). The location of the User Equipment (UE) is tracked at the TAL level. To better capture the "movement locality" of the UE, when the UE leaves the current TAL, the UE is assigned a new TAL whose central TA is the TA where the UE currently resides. This paper investigates the performance of the central-based LTE mobility management scheme, and compares this scheme with the previously proposed central-based mobility management schemes: the movement-based and the distance-based schemes. Our study indicates that under some traffic/mobility patterns, the LTE scheme yields the best performance.